Apparatus for trapping emboli

ABSTRACT

A filter for filtering micro-emboli from a patient&#39;s blood during an angioplasty procedure is disclosed which comprises a plurality of curved wires connected to a rod between a first connector fixed with respect to the rod and a second connector slidingly mounted on the rod. Two layers of filter material are connected to opposite sides of the wires, and each layer includes perforations which are offset from the perforations in the other layer. When the rod and the wires are disposed within a catheter, the inner wall of the catheter compresses the wires toward the rod and when the rod is extended from the catheter, the wires resume their curved shape and pull the sliding connector along the rod toward the fixed connector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/405,445, filed Apr. 1, 2003, which is a continuation of U.S.application Ser. No. 09/511,192, filed on Feb. 23, 2002 and issued onJul. 13, 2004 as U.S. Pat. No. 6,761,727, the entirety of which isincorporated by reference, which is a continuation of U.S. applicationSer. No. 08/921,345, filed on Aug. 29, 1997 and issued on May 9, 2000 asU.S. Pat. No. 6,059,814, which is a continuation-in-part of U.S.application Ser. No. 08/867,531, filed Jun. 2, 1997 and converted into aprovisional application on Aug. 13, 1997, now abandoned.

FIELD OF THE INVENTION

The present application is directed toward a filter, and morespecifically, toward a filter for use during a catheterization procedurefor filtering blood downstream of the procedure site.

BACKGROUND OF THE INVENTION

Arteriosclerosis is a condition in which plaques develop on the innerwalls of blood vessels and restrict the flow of blood there through.Organs downstream of this constriction can be starved of oxygen, and theheart must work harder to pump blood through a circulatory system thatincludes such blockages. When the blockage occurs in the coronaryarteries which feed the heart, a heart attack can result. Similarly,blockages in the carotid arteries can restrict the flow of blood to thebrain with obvious negative consequences.

These blockages are often found in locations that are difficult toaccess. For example, the coronary arteries and some portions of thecarotid arteries are protected by the rib cage. At one time, majorsurgery was required to reach these locations. However, several methodshave been developed for treating plaques in these areas, which methodsinvolve the insertion of a catheter into a patient's blood vessel at alocation that is easy to reach, and guiding the catheter through thevessel toward the blockage. A variety of tools can be passed through thecatheter to treat the blockage, such as lasers or other cutting tools.However one of the more common tools is a balloon which is placed in theconstricted area of the vessel and inflated once or a number of times inorder to push the plaque back against the arterial wall to open theartery. This procedure is called balloon angioplasty and is a commontreatment for arteriosclerosis today.

In order to get a balloon to the location of the blockage, a cathetermust be placed into a patient's artery. This is done by inserting aneedle into an easily accessible artery and threading a guide wirethrough the needle and into the patient's artery. The needle iswithdrawn over this guide wire and an arterial sheath is place over theneedle and into the artery to protect the artery and surrounding tissueduring the procedure. A guiding catheter is placed over the guide wireand maneuvered through the artery to a position near the site of theblockage. When the end of the guiding catheter arrives at a locationnear the blockage, the guide wire is removed, and the catheter isflushed with saline and anchored in place in a suitable manner. Aballoon catheter, having an associated guide wire is then inserted intothe guiding catheter and pushed through the catheter, out of the distalend of the catheter, and guided to the site of the blockage. The guidewire is pushed past the blockage and the balloon is positioned withinthe blockage and inflated to compress the buildup in the artery. Whenthe procedure is complete, the balloon catheter is removed from theguiding catheter and then the guiding catheter is removed as well. Thisprocedure has had a high success rate and is the preferred method fortreating certain types of blockages.

One of the dangers associated with this procedure is that a part of theplaque could break off and enter the patient's blood stream duringtreatment. While no part of the plaque is actually cut away during aballoon angioplasty procedure, small pieces of plaque known asmicro-emboli can and do sometimes break free. These materials are oftentoo large to pass easily through the body's capillaries and can becomelodged therein and block the flow of blood. If the blockage occurs inthe brain or the lungs, it can be harmful or even fatal. Therefore, avariety of techniques are used to stop these particles before theytravel too far.

Heretofore, various filters have been used to trap these particles.Some, such as the filter disclosed in U.S. Pat. No. 4,873,978 toGinsburg comprise a wire mesh for straining objects from thebloodstream. However, this strainer must be inserted into a blood vesselthrough its own opening, downstream from the treatment site and separatefrom the opening used for the balloon catheter or similar device. Thismakes this filter difficult to use and creates additional discomfort forthe patient. Others, such as the filter shown in U.S. Pat. No. 4,425,908to Simon are intended to be permanently attached to the inner wall of ablood vessel. However, it is often desirable to remove the filter aftera procedure is complete, and this would not be practicable using theSimon filter. In addition, the wire mesh strainers disclosed in thesepatents might be capable of stopping relatively large pieces ofmaterial, such as those generated when a plaque is severed from anarterial wall by a cutting instrument, but are not suitable for stoppingthe micro-emboli that can occur during a balloon angioplasty procedure.Neither these nor any other known devices provide a simple and effectiveoption for dealing with such micro-emboli while at the same timefunctioning to block any larger pieces of material that might breakfree. It would therefore be desirable to provide a blood filter fortrapping micro-emboli that could be deployed immediately before aprocedure was commenced and removed shortly thereafter and which couldbe, inserted and removed through the same catheter used in connectionwith the procedure.

SUMMARY OF THE INVENTION

The present invention overcomes these and other problems by providing acompact filter for use alone or as part of an apparatus for performing aballoon angioplasty. The filter comprises a rod slidingly housed withina catheter, and a plurality of curved, flexible wires longitudinallydisposed along the rod and connected thereto at two spaced apartlocations. A portion of filter material is supported by the wires. Whenthe rod is inside the catheter, the wires are held in close proximity tothe rod by the walls of the catheter. When the rod is extended from thecatheter, the wires resume their preformed, curved shape and curve awayfrom the rod. This stretches the filter material across the passagewayto trap any plaques or clots that are present. When the need forfiltration is ended, the rod is pulled back into the catheter. Thisprocess compresses the wires against the rod and closes the filtermaterial around any trapped materials so that they can be removed fromthe body.

In a preferred embodiment of the invention, the flexible wires areattached to two connectors on the outer surface of the rod. Theconnectors are ring-shaped and the wires are evenly distributed aboutthe circumference of the rings. The connector closest to the distal endof the rod (the end inside the patient's body) is slidably connected tothe rod while the proximal connector is fixed. The wires are preformedin a curved shape such that when unbiased by the walls of the catheter,they extend from the proximal connector through an arc that takes themaway from the rod and then back toward the distal connector where theyare also attached. The volume defined by the wires is generally ovoid,and the largest diameter of the volume perpendicular to the axis of therod is selected to be about equal to the diameter of the blood vessel inwhich the filter is to be used. Because the wires are flexible, andbecause the distal connector can slide relative to the rod, when the rodis pulled into a catheter, the wires are compressed toward the rod andthe distal connector is slid along the rod away from the proximalconnector. When the rod is pushed out of the catheter, the distalconnector slides toward the proximal connector and the wires resumetheir preformed shape.

A filter element is attached to the wires to trap material that comesloose from the arterial walls during a procedure. In the preferredembodiment, two layers of a biocompatible material, such as Gortex brandfabric, are used as the filter element with one layer attached to theside of the wires facing the rod and the other attached to the oppositeside so that the wires are sandwiched in-between the two layers. Thematerial extends from the distal connector toward the midpoint of thewires or even slightly further toward the proximal connector. Each layerincludes small perforations to allow fluids to pass while trapping evenvery small emboli. The perforations on the inner sheet are offset fromthose on the outer sheet to better trap and retain emboli. The materialis pulled inwardly toward the rod by the wires when the rod is retractedinto a catheter and is thin enough to fold easily.

The filter can be inserted by itself, but preferably, it is carried onthe same rod used to hold a balloon for a balloon angioplasty procedure.In use, therefore, the balloon catheter will be guided through anarterial narrowing so that its distal end extends beyond the narrowingand so that the balloon is positioned within the narrowing. The rod isthen extended from the catheter to push out the filter a distance ofabout 1 millimeter. After the balloon has been inflated and deflated toenlarge the passageway, the rod and filter are pulled back into thecatheter and the catheter is removed from the body.

The filter also includes safety features to prevent parts of the filteritself from breaking off of the rod. A stop is included on the distalend of the rod which will prevent the slidable connector ring fromsliding all the way off of the rod in the unlikely event that the wiresholding it to the proximal connector should be broken. In addition, asafety wire is attached between the proximal connector and the distalconnector, as well as to the midpoint of the rod there between. Thiswire limits the movement of the distal connector in both directionsalong the rod. By preventing the distal connector from moving too far ina distal direction, it prevents the other wires extending between theconnectors from being stressed. By preventing the distal connector frommoving too far in the proximal direction, it limits the diameter of theovoid volume defined by the curved wires so as not to damage the vesselwalls that surround the filter.

It is therefore a primary object of the present invention to provide anapparatus for filtering a fluid in a bodily passageway.

It is another object of the present invention to provide a filteringdevice for filtering blood flowing through a blood vessel.

It is a further object of the present invention to provide a collapsiblefiltering device which can be passed through a narrowing in a bloodvessel and then expanded to its functional size on the other side of thenarrowing.

It is yet another object of the present invention to provide a filteringdevice which can be inserted into a blood vessel through a catheter.

It is yet a further object of the present invention to provide afiltering device that can be attached to an instrument used during anangioplasty procedure.

It is still another object of the present invention to provide a filtersuitable for trapping both large and small particles of material in thebloodstream.

It is still a further object of the present invention to provide afiltering device that can be deployed and retracted in a simple mannerfrom a remote location.

It is yet another object of the present invention to provide a filterfor use in conjunction with a catheter which filter is shifted betweenfunctional and storage configurations by sliding it into and out of thecatheter.

It is another object of the present invention to provide a filter thatcan be deployed and retracted by sliding the filter support relative toa tubular member such as a catheter.

It is yet another object of the present invention to provide a filteringapparatus that includes safety features to help prevent portions of theapparatus from separating from the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects will become evident from a reading andunderstanding of the following detailed description of a preferredembodiment of the invention together with the following drawings ofwhich:

FIG. 1 is an elevational view of a filter apparatus according to thepresent invention showing the filter in its fully open conditionextending out of a balloon catheter;

FIG. 2 is a pictorial view, partly in section, of the filter of FIG. 1collapsed within a catheter;

FIG. 3 is a pictorial view, partly in section, of the subject filterextending part of the way out of a catheter; and,

FIG. 4 is a pictorial view, partly in section, of the subject filter inits fully open condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, wherein the showings are for the purposeof illustrating a preferred embodiment of the subject invention only andnot for the purpose of limiting same, FIG. 1 shows a balloon catheterassembly designated generally by the numeral 10 positioned within anartery 12 having walls 14 wherein blood flows in the direction of arrow13. Plaques 16 on walls 14 decrease the diameter of artery 12, and thepurpose of the angioplasty procedure is to compress plaques 16 againstwalls 14 to increase the blood flow through artery 12. Catheter assembly10 comprises a balloon catheter 18 having an outer wall 20, an innerwall 21, a lumen 22 and a distal end wall 24 at its distal end 26. (Inthis description, the term “distal” refers to the end of the catheterassembly deep within the patient's body and the term “proximal” refersto the end of the assembly outside of the patient's body). A balloon 23is connected to outer wall 20 of catheter 18 and is equipped withsuitable inflation means (not shown) to cause the balloon to expandagainst plaques 16. The use of a balloon for this purpose is well knownand the mechanism for inflating and deflating the balloon does notcomprise a part of the present invention. A rod 28, preferably made fromNitinol or titanium, is disposed within lumen 22 for sliding movementwith respect to catheter 18 and includes an outer wall 30, a lumen 32,and a distal end 34. The rod has an outer diameter and an innerdiameter. A guide wire 36 is housed within lumen 32 for sliding movementwith respect to rod 28. Rod 28 includes a stop 38 mounted on outer wall30 near distal end 34 and a filter assembly designated generally by thenumeral 40 mounted on outer wall 30 proximally of stop 38.

Filter assembly 40 comprises a proximal ring connector 42 and a distalring connector 44 located between proximal connector 42 and stop 38.Each ring has an outer diameter and an inner diameter. Proximal ring 42is fixedly connected to outer wall 30 while distal ring 44 is free toslide longitudinally along the outer wall of rod 28. Twelve flexiblewires 46 are connected between rings 42 and 44 such as by welding themto the connectors. This number of wires has been found to providesatisfactory performance, but a greater or lesser number of wires couldbe used if desired. These wires are preformed to have a curved shape sothat when connected between connectors 42 and 44 they arc outwardly fromthe rod a distance sufficient to bring them into contact with the wallof the vessel in which the filter is used. More specifically, the wiresare curved so that the diameter of a section taken perpendicular to rod28 and through a midpoint 48 of the wires is approximately equal to orslightly larger than the diameter of artery 12. In this manner, it isassured that the midpoints 48 of the wires will be pressed firmlyagainst the wall 14 of artery 12 when the filter is deployed as will bedescribed hereinafter. These wires are uniformly spaced about thecircumferences of rings 42, 44, extend generally parallel to each other,and are preferably made from a titanium wire. When in its operativeposition, filter assembly 40 is approximately 4 millimeters long fromring 42 to ring 44.

Filter assembly 40 also includes a first layer of filter material 50secured to wires 46 on the side of wires 46 facing rod 28 and a secondlayer of filter material 52 secured to wires 46 on the side of the wiresopposite from first layer 50. Layers 50 and 52 extend from distal ring44 to approximately midpoints 48 of wires 46 or a point slightly closerto proximal ring 42 than midpoint 48. The preferred material for formingthese filter layers is Cortex brand fabric because of its ability towithstand the conditions present in the bloodstream and because it isswell tolerated by the body. Other similar materials could readily besubstituted therefor. Each layer 50, 52 includes a plurality ofperforations 54 which perforations are evenly distributed over thesurface of each sheet. The sheets are arranged, however, so that theperforations in the sheets are not aligned. These perforations allow forimproved blood flow through the filter, while still allowing the filterto trap and retain very small micro-emboli.

Rings 42 and 44 have an outer diameter less than the inner diameter ofballoon catheter 18 and slide freely within lumen 22. The diameter offilter assembly 40 at midpoints 48 is substantially greater than theinner diameter of catheter 18, and, except in the immediate vicinity ofrings 42, 44, the cross section of wires 46 normal to rod 28 is alsogreater than the inner diameter of the catheter. Therefore, when rod 28is drawn into catheter 18, proximal ring 42 passes into lumen 22 butwires 46 come into contact with distal end wall 24. Because the wiresare flexible, however, they are compressed toward rod 28 by end wall 24as the filter assembly 40 moves into lumen 22. As the wires are forcedtoward rod 28, they push distal ring 44 away from proximal ring 42.Distal ring 44 continues to slide in this direction until midpoints 48of wires 46 are drawn past distal end wall 24. After this point, theremaining portion of filter assembly 40 can be drawn into lumen 22 whilering 44 remains in essentially the same position. Stop 38 has an outerdiameter smaller than the inner diameter of catheter 18 and also passesfreely into the catheter along with rod 28. These steps are reversedwhen rod 28 is pushed out of catheter 18. Stop 38 and distal ring 44exit past distal end wall 24 of catheter 18 and wires 46 continue to beheld in the orientation they assumed when inside the catheter, generallyparallel to rod 28 and generally evenly spaced therefrom along theirentire lengths. As midpoints 48 exit the catheter, wires 46 begin toreturn to their preformed, curved shape and spread away from rod 28 inall directions. This in turn pulls distal ring 44 back toward proximalring 42 until proximal ring 42 has moved outside of the catheter.

Catheter assembly 10 also includes a number of safety features to ensurethat, even if the device is damaged during use, parts thereof will notbreak off and enter the bloodstream. First, wires 46 are all made fromtitanium which does not react with water or the chemicals present in theblood stream. In addition, titanium has great strength for per unitweight which reduces the chance that the wires will break during normaluse. Wires 46 are each fastened to both rings by welds and thereforeboth ends of the wires will remain attached to a structure even if awire breaks. In the unlikely event that all of wires 46 break, or thatthey all become detached from distal ring 44, stop 38 will prevent ring44 from sliding off of rod 28 and into the bloodstream. Finally, asafety wire 56 is connected between proximal ring 42 and distal ring 44and also welded to rod 28 at a central point there between. Wire 56limits the range of movement of distal ring 44 and is fully extendedalong rod 28 when wires 46 are pressed against rod 28. This wireprovides added protection to retain distal ring 44 on rod 28. Wire 56also provides a biasing force to help prevent distal ring 44 from comingtoo close to proximal ring 42. These safety features help to ensure thatthe subject device functions properly during use.

To use the subject filter, rod 28 is inserted into lumen 22 of catheter18 and positioned so that filter assembly 40 is located generallyinteriorly of balloon 23. Guide wire 36 is inserted into lumen 32 toallow balloon catheter 18 to be steered through a patient's bloodvessels. The entire assembly is coated with heparin to reduce clotformation during the procedure. A needle is next inserted into an easilyaccessible artery and a guide wire (not shown) is threaded through theneedle and into the patient's artery. The needle is withdrawn over thisguide wire and an arterial sheath is placed over the guidewire and intothe artery to protect the artery and surrounding tissue during theprocedure. A guiding catheter, also coated with heparin, (not shown) isplaced over the guide wire and maneuvered through the artery to aposition near the site of the blockage. At this point the guide wire isremoved and the catheter is flushed with saline solution. Ballooncatheter 18 with filter assembly 40 housed within, is next insertedthrough the guiding catheter and out of the distal end thereof. Fromthis point, guide wire 36, which extends beyond rod 28 and out ofcatheter 18, is used to steer the catheter to the site of the blockage.The fact that distal ring 44 is slidingly attached to rod 28 makes iteasier to navigate the tortuous pathway through the bloodstream to thesite of the blockage or narrowing. When ring 44 contacts the wall of anartery, for example, it can easily slide out of the way and this reducesthe need for backing up and repositioning the catheter during theinsertion process. Guide wire 36 is passed through the narrowed part ofthe artery and balloon 23 is positioned in this narrowing. Rod 28 isthen extended from catheter 18 so that proximal ring 42 is spaced about1 millimeter distally of distal end wall 24. Wires 46 have been chosenbased on the size of artery 12 and press firmly against wall 14 of theartery which in turn holds filter elements 50 and 52 against the wall.

To help locate the filter assembly during an angiographic procedure,radiopaque markers 58 are placed on both the proximal and distal rings.Additional radiopaque markers 60 and 62 are placed on shaft 28 andanother marker 64 is placed at the end of catheter 18. Marker 60 islocated at the end of shaft 18 and, when aligned with marker 64, showsthat the distal end of rod 28 is at the end of catheter 18. The secondrod marker 62 is located proximally of filter assembly 40, and whenmarker 62 is aligned with marker 64 indicates that the filter assemblyhas exited the catheter.

The balloon is inflated once or a number of times to compress plaque 16against the arterial wall. During this procedure, blood is flowing pastthe plaque and balloon and micro-emboli which form will flow towardfilter apparatus 40 and be trapped therein. When the compression of theplaques is complete, rod 28 is pulled back into catheter 18 along withany particles trapped by the filter. Using standard techniques, it isalso possible to leave the filter in place temporarily while the ballooncatheter is removed and replaced with a stent, a stent catheter balloon,or a balloon of a different size. To do this, an exchange length wire ofapproximately 300 centimeters must be used. This requires that shaft 28be of this exchange length as well. When this procedure is complete, thefilter is withdrawn into the lumen of whichever catheter is in place.

The invention has been described herein in terms of a preferredembodiment and many changes and modifications will become obvious to theskilled practitioner upon a reading and understanding of the foregoingdescription and an examination of the drawings. It is intended that allof these modifications be included within the scope of this invention tothe extent that they are defined by the several claims appended hereto.

1. An apparatus for trapping emboli in the vessel of a patient, theapparatus comprising: a rod having an axis and a distal end that isinsertable into the vessel; a trapping element disposed adjacent the roddistal end and having proximal and distal ends connected to the rod atspaced-apart locations, at least one of the proximal and distal ends ofthe trapping element being slidably connected to the rod, and whereinthe trapping element is diametrically retractable about the rod anddiametrically expandable away from the rod; and a stop mounted on therod spaced from the proximal and distal ends of the trapping elementconfigured to prevent distal sliding of the at least one of the proximaland distal ends of the trapping element slidably connected to the rodwhen the trapping element is both expanded and retracted.
 2. Theapparatus of claim 1, wherein the stop is mounted on the rod distally ofthe distal end of the trapping element when the trapping element is bothexpanded and retracted.
 3. The apparatus of claim 1, wherein thetrapping element comprises a filter.
 4. The apparatus of claim 1,wherein the filter comprises a plurality of flexible strands.
 5. Theapparatus of claim 4, wherein the filter further comprises a perforatedmaterial supported by the flexible strands.
 6. The apparatus of claim 1,wherein the trapping element has been preformed to define an ovoidvolume.
 7. The apparatus of claim 1, further comprising a catheterhaving a lumen slidingly disposed about the rod.
 8. The apparatus ofclaim 7, wherein the catheter is slidingly movable over at least aportion of the trapping element for compressing the element towards therod.
 9. The apparatus of claim 1, wherein the trapping element distalend is fixedly connected to the rod.
 10. The apparatus of claim 1,wherein the trapping element proximal end is fixedly connected to therod.
 11. An apparatus for trapping emboli in the vessel of a patient,the apparatus comprising: a rod having an axis and a distal end that isinsertable into the vessel; a trapping element disposed adjacent the roddistal end and having proximal and distal ends, at least the distal endof the trapping element being slidably connected to the rod, and whereinthe trapping element is diametrically retractable about the rod anddiametrically expandable away from the rod, the trapping element beingpreformed in its expanded shape.
 12. The apparatus of claim 11, whereinthe proximal and distal ends of the trapping element comprise radiopaqueconnectors.
 13. The apparatus of claim 11, further comprising a catheterslidably arranged around the rod and having proximal and distal ends,the distal end of the catheter being slidable over the trapping elementto diametrically retract the trapping element.
 14. The apparatus ofclaim 11, wherein the trapping element is a filter.
 15. The apparatus ofclaim 11, wherein the proximal and distal ends of the trapping elementare connected about the rod with rings.
 16. The apparatus of claim 15,wherein the rings are radiopaque.